When disaster strikes, effective telecommunications for emergency response personnel involved in recovery efforts is essential. Since telecommunications capability can be severely affected due to excessive traffic in a disaster situation, loss of infrastructure and potential denial of service attacks, certain features can be included in the telecommunications network to enable and facilitate emergency response communications.
One such feature is the Government Emergency Telephone Service (GETS). GETS is a set of switch-based and Advanced Intelligent Network (AIN) features which allow authorized users to gain access to enhanced call completion features, including Alternate Carrier Routing, High Probability of Completion (HPC), HPC Detection and SS7 IAM Message Priority, HPC Trunk Queuing, HPC Exemptions From Network Management Controls, Enhanced Alternate Carrier Routing, and Default Routing. To gain access to GETS, a user first dials an access number, then enters an authentication PIN, and then enters the desired destination number. GETS operates on the major long-distance carrier networks, most local networks, including wire-line, cellular and PCS systems, and government-leased networks such as the Federal Telecommunications System (FTS2000) and the Defense Information System Network (DISN). Thus, GETS access is available from most every telephone line in the country.
Another related feature is Essential Line Service (ELS). ELS is a switch-based feature that allows priority access to dial tone when the switch is in certain overload conditions. Typically, telephone lines associated with “911” service, police, fire, ambulance and other emergency services are designated as ELS lines, commonly referred to as “class A” lines, with the remaining lines referred to as “class B” lines. As the switch becomes overloaded, certain controls are activated. Eventually, the switch denies dial tone to all but class A lines. The switch may then move in and out of the overload condition as a result of shedding new call attempts from class B lines, but can remain in overload for a significant period of time.
With ELS, emergency related lines are identified early on as part of a planning process, and these lines are engineered in the switch to be class A lines. GETS, on the other hand, is a “portable” service in that a GETS call may be placed on any available line without requiring the line to have been previously engineered for special treatment.
There is a problem with GETS during periods of heavy use and overload conditions in that a user desiring to place an emergency related GETS telephone call from a class B line during a switch overload condition may have to wait a very significant amount of time before receiving dial tone. The caller has to remain off-hook until the switch is no longer in ELS overload before the switch will again begin to process class B line origination attempts. Alternatively, the caller may periodically go off-hook and listen for dial tone.
It would be desirable for a class B line that places a GETS call to be temporarily dynamically designated as a class A line on the assumption that the next call made from the line will likely also be emergency related.